Apparatus for defrosting evaporator of a refrigeration unit

ABSTRACT

An apparatus is provided for defrosting the evaporator coils of a conventional refrigeration unit by passing hot compressed refrigerant gas to the evaporator coil prior to any cooling, condensing or expansion of the refrigerant gas. Thereafter the refrigerant gas is condensed, expanded and recompressed for recycle for the process and apparatus.

United States Patent Okutus 51 May 30, 1972 [s41 APPARATUS FORDEFROSTBQG 2,694,904 1111954 Lange .s2/27s EVAPORATOR OF A REFRIGERATION2,916,893 12/1959 Kramer... .....62/278 I 3,195,321 7/1965 Decker..62/278 [72] Inventor: Teruhiko Okutus, l, 18 Higashi Maitocho,Minami-ku, Yokohama, Japan [22] Filed: Apr. 23, 1970 [21] Appl.No.:31,249

521 u.s.c1. ..62/196, 62/278 [51] lnt.Cl. ..F25b4l/00 [581 Field 01Search ..62/ 196, 278

[56] References Cited UNITED STATES PATENTS 2,530,440 11/1950 Nussbaum..62/278 UNIT W19 Til? aarz. Er 1' 7 Primary Examiner-Meyer PerlinAttorney-Cushman, Darby & Cushman [57] ABSTRACT 1 Claim, 1 DrawingFigureZa I W475! ON 7457' M69753 l/YLET a Patented May 30, 1972 I I 3,665,723

W075? OUTLET 11/ 97517 l/YLET Con/054 55 INVENTOR /QQM APPARATUS FORDEFROSTING EVAPORATOR OF A REFRIGERATION UNIT The present inventionrelates to an apparatus for defrosting the evaporator coils of aconventional refrigeration unit. More particularly, the inventionrelates to an apparatus for applying heat to the evaporator coils of aconventional refrigeration unit to melt and vaporize frost which isformed on the evaporator coils.

As is well known in the art, the evaporator coils of a refrigerationunit will accumulate frost, i.e., condensed and frozen moisture vapor,after a period of operating time and when the evaporator coils areoperated at a temperature below the freezing point of water. Theseconditions are encountered in both domestic and industrial refrigeratorswhich are used for storing various materials, e.g., food, chemicals etc.

l-leretofore, the frost accumulated on the evaporator coils ofconventional refrigeration units has been removed either by hand or byapplying electrical heat to the evaporator coils for melting andvaporizing the frost. Conventionally, when it is necessary to removefrost from the evaporator coils, the refrigeration operation is stopped(e.g. the compressor at least) and electrical heat is applied to theevaporator coils by means of resistance or like heaters. Optionally,resistant heaters can be used to heat an airstream which is in turnblown across the evaporator coils. The net effect of any of thesesystems, however, is the disruption of the operation of the compressorof the refrigeration unit.

For many cases, it is desirable not to disrupt the compressor operationbut to keep the compressor in substantially continuous operation. Inthese cases, it would be desirable if the evaporator coils of aconventional refrigeration apparatus could be cleared of frost withoutdisrupting the compressor operation. While the compressor operationcould be continued even during an electrical heating of the evaporatorcoils to remove the frost, the compressor would, in eifect, be buckingthe heat applied to the evaporator coils and would result in a grosslyinefficient operation.

lt is an object of the present invention to eliminate the difficultiesand disadvantages noted above in connection with the use of electricalheat for removing frost from evaporator coils and to provide a processand apparatus to accomplish the same.

The invention has as its basis, the discovery of a means of vusing thecompressor of a conventional refrigeration apstated, the presentinvention resides in the use of compressed refrigerant gas, which hasbeen heated during compression, for supplying heat to the evaporatorcoils for defrosting the evaporator coils. Preferably, the heated,compressed gas is passed through the evaporator coils in a directionopposite to that which the gas is passed through the evaporator coilsduring a cooling cycle.

For a full description of the invention and a detailed embodimentthereof, attention is now directed to the drawing where the FIGURE showsin diagrammatic illustration a conventional refrigeration apparatuswhich has been modified according to the present invention.

In the FIGURE, there is shown a cooling unit 1 containing a conventionalevaporator coil 1a which would correspond to, for example, aconventional freezer having an evaporator coil in an operable relationthereto. A conventional electrically driven compressor 2 operates tocompress a refrigerant gas (any conventional refrigerant gas, such asthe Freons, may be used) and the compressor is in communication with theevaporator coil la via compressor discharge conduits 2a, 2b and 20.Between compressor conduits 2a and 2b is disposed condenser 3 forcooling and condensing the refrigerant gas compressed by compressor 2.In other words, this is a conventional condenser coil. The condenser 3may, optionally, be cooled by blowing air over the heat exchangersurfaces by means of a fan or like device, but preferably the condenseris cooled by a flow of water, in a conventional manner, as noted in thedrawing. The compressor, condenser and evaporator coil are operated in aconventional manner whereby refrigerant gas is compressed in compressor2, condensed to a liquid in condenser 3, passed through an expansionvalve 4, of conventional design, and allowed to evaporate in theevaporator coil 1a of cooling unit 1 to cool the cooling unit. Theevaporated refrigerant is returned to the compressor via return conduitslb and 1c to compressor 2. In order to ensure that all of therefrigerant entering compressor 2 is in the gaseous phase, it may passthrough a heat exchanger 5. The evaporated refrigerant is thereforerecompressed in compressor 2 and the operation is continued in aconventional manner to produce cooling in cooling unit 1. All of theabove simply il lustrates a conventional refrigeration unit and nofurther detail or discussion thereof is required.

After cooling of the cooling unit 1 is carried out for a sufficientlength of time that frost has been formed on the evaporator coil In ofcooling unit 1, the frost is removed by performing the followingoperation. Valve V2, which is open during the cooling operation and isdisposed in the return conduit, is closed, and valves V1 and V3, whichare closed during the cooling operation, are opened. With these valveposition arrangements, the compressed high-pressure gas leavingcompressor 2 flows through valve Vl, as shown by the dashed arrow,instead of going through condenser 3, as shown by the solid-line arrow.The gas does not go through condenser 3 as a result of the back pressureexerted by expansion valve 4 on the refrigerant in the conduit leavingcondenser 3. The hot, compressed refrigerant gas passes through conduitlb, as shown by the dashed arrows, and into cooling unit 1 andevaporator coil 1a. Since the evaporator coil is cold, due to thecondensed and frozen moisture thereon, the evaporator coil will cool thehot refrigerant gas and at least partially condense the same. However,this exchange of heat causes the frost on the evaporator coil to meltand vaporize. The at least partially condensed refrigerant passesthrough evaporator coil 1a and to valve V3, as shown by the dashed arrowat conduit 2c. After the refrigerant passes through valve V3, it isexpanded through expansion valve 7 and is allowed to vaporize as itpasses through conduit 8 located in heat exchanger 5. After vaporizationin conduit 8, the vaporized refrigerant passes into cooling coils 6 viaconduit 6a, as shown by the dashed arrow. The refrigerant issubstantially completely vaporized while passing through cooling coil 6and then passes, as shown by the dashed and solid arrows, via conduit1c, back to the intake (low-pressure side) of compressor 2. The gas isthen compressed (and heated during compression) in the manner describedabove and recirculated through evaporator coil 1a to further melt and/orevaporate frost condensed on that coil.

After all of the frost has been melted and/or evaporated or otherwiseremoved from the cooling unit 1, as by draining away the meltedmoisture, the cooling operation in cooling unit 1 is again commencedsimply by closing valves V1 and V3, while opening valve V2. Valves V1,V2 and V3 may be manually operated, if desired, or those valves may beautomatically operated on a timed sequence or they may be actuated via afrost-sensing device on evaporator coil In, such devices beingconventional and known in the art.

As can be seen from the above, the apparatus described can be changedfrom a cooling mode in the cooling unit to a defrosting mode in thecooling unit simply by changing the flow position of three valves andwithout any disruption of the compressor operation.

As noted above, cooling water may be used in the cooling condenser 3,and as noted in the figure, that cooling water may also circulatethrough heat exchanger 5 before being ultimately discharged. However, asis quite apparent, no cooling water may be used, condenser 3 and heatexchanger 5 may have separate cooling water sources, or instead ofwater, cooling unit 1 and/or heat exchanger 5 may use a coolant otherthan water.

As discussed above, cooling coils 6 are disposed in heat exchanger and,optionally, the cooling water from condenser 3 may be circulated overthe exterior surfaces thereof. One result of this arrangement is thatthe refrigerant which passes through valve V2 in the normal coolingoperation will be thoroughly vaporized and can be fed to compressor 2without the normal holding tanks and like devices for separating liquidand gas, as is normally required in conventional refrigerationapparatus.

As is quite apparent from the above description, the apparatus of theinvention utilizes conventional components and the invention resides inthe combination of these conventional components and the manner of usethereof. Hence, any conventional materials and designs of the individualcomponents are acceptable to the present invention so long as thematerials and designs function in the manner described. For example,conventional steel, aluminum or copper conduits may be used in theevaporator and cooling coils, as well as for transporting therefrigerant. Optionally, the coils may be finned coils, if desired.

Hence, the above describes an apparatus for defrosting the evaporatorcoil of a refrigeration unit by disrupting the flow of compressedrefrigerant gas from the high-pressure side of a compressor to theevaporator coil, passing hot, compressed refrigerant gas through theevaporator coil, preferably in an opposite direction to that directionused during the cooling cycle, causing heat exchange from the hotcompressed refrigerant gas to the frost on the evaporator coil, therebymelting and vaporizing frost, removing the cooled and at least partiallycondensed refrigerant from the evaporator coil, passing the cooledrefrigerant through an expansion valve, expanding the refrigerant in aheat exchanger and thereby vaporizing the refrigerant, compressing thevaporized refrigerant, and returning the hot, compressed refrigerant gasto the evaporator coil in the cyclic mannervof the foregoing steps tomelt and evaporate the frost on the evaporator coil.

While the principles of the invention were hereinbefore described withreference to the drawing and preferred embodiment, the specificillustrations of the invention are intended to only exemplify, ratherthan limit, the invention, and the invention is applicable to the extentdescribed above, and as defined in the claims.

What is claimed is:

1. In a refrigeration unit comprising a compressor, condenser, expansionvalve and evaporator coil, each of which is operably connected in thenamed conventional order by conduit means for flowing a refrigeranttherethrough in a conventional path, the improvement comprising:

1. conduit means connecting the discharge side of the compressor withthe evaporator coil for passing compressed and heated refrigerant gasthrough the evaporator coil, whereby the refrigerant gas is cooled andat least partially condensed and frost on the evaporator coil is melted;

2. conduit means connecting the evaporator coil with a second expansionvalve for transporting the cooled and at least partially condensedrefrigerant to the second expansion valve;

3. heat exchanger means, connected by a conduit to said expansion valve,for evaporating the expanded, cooled and partially condensedrefrigerant, whereby the refrigerant becomes substantially completelygaseous;

4. conduit means connecting the heat exchanger means with the compressorfor returning the gaseous refrigerant to the intake side of thecompressor;

5. valve means for disrupting the said conventional path of refrigerantand providing the path of refrigerant defined by elements 1) through 4);

6. means for circulating water about the condenser;

7. conduit means connecting the condenser and heat exchanger means forpassing the water from the condenser to the heat exchanger; and meansfor circulating the water about the heat exchanger means.

1. In a refrigeration unit comprising a compressor, condenser, expansionvalve and evaporator coil, each of which is operably connected in thenamed conventional order by conduit means for flowing a refrigeranttherethrough in a conventional path, the improvement comprising: 1.conduit means connecting the discharge side of the compressor with theevaporator coil for passing compRessed and heated refrigerant gasthrough the evaporator coil, whereby the refrigerant gas is cooled andat least partially condensed and frost on the evaporator coil is melted;2. conduit means connecting the evaporator coil with a second expansionvalve for transporting the cooled and at least partially condensedrefrigerant to the second expansion valve;
 3. heat exchanger means,connected by a conduit to said expansion valve, for evaporating theexpanded, cooled and partially condensed refrigerant, whereby therefrigerant becomes substantially completely gaseous;
 4. conduit meansconnecting the heat exchanger means with the compressor for returningthe gaseous refrigerant to the intake side of the compressor;
 5. valvemeans for disrupting the said conventional path of refrigerant andproviding the path of refrigerant defined by elements (1) through (4);6. means for circulating water about the condenser;
 7. conduit meansconnecting the condenser and heat exchanger means for passing the waterfrom the condenser to the heat exchanger; and means for circulating thewater about the heat exchanger means.
 2. conduit means connecting theevaporator coil with a second expansion valve for transporting thecooled and at least partially condensed refrigerant to the secondexpansion valve;
 3. heat exchanger means, connected by a conduit to saidexpansion valve, for evaporating the expanded, cooled and partiallycondensed refrigerant, whereby the refrigerant becomes substantiallycompletely gaseous;
 4. conduit means connecting the heat exchanger meanswith the compressor for returning the gaseous refrigerant to the intakeside of the compressor;
 5. valve means for disrupting the saidconventional path of refrigerant and providing the path of refrigerantdefined by elements (1) through (4);
 6. means for circulating waterabout the condenser;
 7. conduit means connecting the condenser and heatexchanger means for passing the water from the condenser to the heatexchanger; and means for circulating the water about the heat exchangermeans.